1. Field of the Invention
The invention relates to the fields of medical instruments, and more particularly, to a hand-held dental instrument for drilling teeth.
2. Background of the Invention
High-speed turbine dental drill handpiece is an instrument for drilling teeth. It is inserted into the oral cavity of a patient and touches parts in the oral cavity such as teeth, oral mucosa, etc. As shown in FIG. 1, an existing high-speed turbine dental drill handpiece comprises a head 4, a drilling needle 3, a button cap 9, a front handle 1, and a back handle 2. The front handle 1 and the back handle 2 are held by hand during application. The rear portion of the back handle 2 is connected with a quick disconnect adapter. The quick disconnect adapter is connected to water and air lines of the dental unit. The supplied compressed air provides rotation power for the handpiece, and the supplied pressure water serves to cool the cutting position. When the drilling needle 3 is drilling teeth at a high-speed, it must be cooled with water. When drilling teeth, water saliva, and drilling sludge form contamination fluid. If the patient carries some transmissible disease such as hepatitis, AIDS, etc., the contamination fluid may contain dangerous pathogens. It is well known that a fluid suckback phenomenon will occur when the existing high-speed dental drill handpiece is drilling teeth. As shown in FIG. 2, when the powered wind wheel 7 is rotating, air for cooling the bearing flows out from the clearance space 17 between the bearing 6, the wind wheel axle 15, and the head housing 4. At this point, the air pressure inside of the head housing is higher than the atmospheric pressure, thus no suckback phenomenon occurs. However, when the drilling needle stops rotating, the powered wind wheel will still rotate for a certain time due to rotatory inertia. Since no compressed air to the air supply orifice 12 is supplied at that time, air is supplemented from the core portion of the wind wheel and flows into the head housing, and then discharges from the exhaust outlet of the head housing into the inner cavity of the handpiece handle and the behind exhaust passage, as shown in FIG. 3. At this time, if the contaminated fluid touches the front part of the head, the contaminated fluid will flow into the head housing 18, which is termed fluid suckback phenomenon. When the handpiece starts to operate again, the contaminated fluid sucked in the head will be pushed out from the head housing. This phenomenon will be repeated each time the drill stops and starts rotating. The contaminated fluid contaminates not only the handpiece, but also the adapter and pipelines. When using the same handpiece with another patient, the contaminated fluid will spray into the oral cavity of the patient, resulting in an iatrogenic cross infection.